1. Technical Field
The present invention relates to a liquid crystal device and an electronic apparatus, and more particularly, to an electrooptical device including a transmissive display region and a reflective display region in each sub-pixel.
2. Related Art
In general, liquid crystal devices have a cell structure in which liquid crystal is sealed between a pair of substrates, and an alignment film is provided on each of the substrates to regulate the initial alignment state of the liquid crystal. The alignment film is formed, for example, by applying unset resin, such as polyimide, onto the inner surface of each of the substrates by spin coating or printing, and drying or baking the resin.
Liquid crystal devices usually adopt a transmissive display method using transmitted light from a backlight, and a reflective display method using reflected external light. In particular, most mobile electronic apparatuses include a transflective liquid crystal device capable of transmissive display and reflective display. In a transflective liquid crystal device, sub-pixels are arranged in an effective driving region. Each of the sub-pixels includes a transmissive display region capable of transmissive display with a backlight, and a reflective display region capable of reflective display with external light.
In the transflective liquid crystal device, transmitted light for transmissive display passes through a liquid crystal layer only once, whereas reflected light for reflective display passes through the liquid crystal layer twice. Therefore, the degree of retardation of display light caused by the liquid crystal layer substantially differs between transmissive display and reflective display. In order to reduce the difference in retardation between the transmissive display and the reflective display, the thickness of the liquid crystal layer in the reflective display region is usually set to be smaller than the thickness in the transmissive display region.
More specifically, the thickness of the liquid crystal layer is controlled by forming an insulating film on only a part of the inner surface of the substrate. That is, as disclosed in JP-A-2003-248222, a thick insulating film is provided in the reflective display region of the sub-pixel, and an insulating film is not provided or a thin insulating film is provided in the transmissive display region, so that the thickness of the liquid crystal layer sandwiched between the substrates is made different between the reflective display region and the transmissive display region.
However, in the above-described transflective liquid crystal device, the insulating film is locally provided on the substrate, when an unset resin is applied on the substrate, it collects on regions where the insulating film is not provided (transmissive display regions). Consequently, the thickness of the alignment film becomes nonuniform, and display quality is lowered. Accordingly, JP-A-2004-325822 discloses that each recessed transmissive display region continuously extends through the adjoining pixels in order to enhance the fluidity of the alignment resin and to reduce nonuniformity of the thickness of the alignment film (particularly in FIGS. 3 and 13 to 17).
In the above-described improved liquid crystal device, fluidity of the alignment resin is enhanced because the recessed transmissive display region continuously extends through the pixels, whereas the problem of the nonuniform thickness of the alignment film is sometimes not solved satisfactorily. For example, when an insulating film is patterned such that a reflective display region is also formed such as to continuously extend through pixels, the reflective display region is interposed between continuous transmissive display regions. Therefore, the alignment resin entering from the reflective display region scatters in the extending direction of the transmissive display regions. Particularly at a peripheral edge of the transmissive display region close to the reflective display region, the thickness of the alignment film becomes nonuniform, and display quality is lowered. Further, when the alignment resin is applied by printing, degradation of display quality is sometimes inevitable, depending on the relationship between the printing direction and the extending direction of the transmissive display region.
A technique of forming an island-shaped reflective display region in each pixel is also adopted in the above-described liquid crystal device. In this case, a groove is provided between reflective display regions. Since the alignment resin can flow laterally and longitudinally (horizontally and vertically), it can be thought that nonuniformity of the thickness of the alignment film can be reduced. However, since the peripheral edge of the reflective display region is long compared with the area of the reflective display region, alignment defects of liquid crystal are easily caused by a height difference formed at the peripheral edge of the reflective display region, and display quality is lowered.